import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class Solution {
    public List<List<Integer>> threeSum(int[] nums) {
        Arrays.sort(nums);
        List<List<Integer>> result = new ArrayList<>();
        int n = nums.length;
        if(n < 3){
            return result;
        }
        for (int i = 0; i < n-2; i++) {
            //去重
            if(i > 0 && nums[i-1] == nums[i]) continue;

            int left = i+1, right = nums.length - 1;
            while(left < right){
                int sum = nums[i] + nums[left] + nums[right];
                if(sum < 0){
                    left++;
                } else if (sum > 0){
                    right--;
                } else {
                    List<Integer> list = new ArrayList<>();
                    list.add(nums[i]);
                    list.add(nums[left]);
                    list.add(nums[right]);
                    result.add(list);

                    //去重
                    while(left < right && nums[left] == nums[left + 1]){
                        left++;
                    }
                    while(left < right && nums[right] == nums[right - 1]){
                        right--;
                    }
                    left++;
                    right--;
                }
            }

        }


        return result;
    }
}
